The big migrations of the nineteenth and twentieth century may be looked upon primarily as a social or as an economic or as a political phenomenon, or as a combination of all three, with each of the major waves of migration having another of these three characteristics as its most conspicuous element. The first real mass migration was that of the “Potato Irish” in the middle of the nineteenth century. Between 1956 and 1960 a total of 2.9 million people immigrated to what used to be the domain of European migration: the United States, Canada, Australia, and New Zealand. Simultaneously with this dramatic increase in numbers came a shift in regions of origin: from the former predominance of immigration primarily from northern and western Europe to a predominance of immigration from southern and eastern Europe.